1. Technical Field
The present invention generally relates to an image forming apparatus, such as, a copier, a printer, a facsimile machine, a plotter, or a multifunction peripheral (MFP) including at least two of coping, printing, facsimile transmission, plotting, and scanning capabilities, and further to a process cartridge used in the image forming apparatus.
2. Description of the Background Art
There are image forming apparatuses that charge a photoreceptor serving as a an image bearer, expose the photoreceptor, thereby forming an electrostatic latent image, develop the electrostatic latent image with toner into a toner image, and transfer the toner image onto a sheet of recording media. After the toner image is transferred therefrom, the photoreceptor is cleaned as a preparation for subsequent image formation.
For example, to charge the photoreceptor, voltage is applied to a charging device, such as a charging roller including a metal core and a conductive elastic layer overlying the metal core, and the charging roller is disposed in contact with the photoreceptor that rotates. It is preferred that the charging device have stable charging characteristics and be highly resistant to contamination of the photoreceptor with, for example, toner. Further, it is preferred that the charging device do not contaminate the photoreceptor.
For example, JP-2011-095725-A proposes making the surface of the charging roller uneven with projections and recesses extending in the circumferential direction of the charging roller. Specifically, projections having a predetermined width and extending in the circumferential direction are formed in the surface of the charging roller discontinuously, thereby forming recesses, shaped like slots extending in the circumferential direction, between the projections. In such a charging roller, toner can pass through the recesses in the surface, and toner is less likely to be caught on the surface. This configuration can inhibit contamination of the charging roller and secure the charging characteristics for a long time.
To clean the photoreceptor, that is, remove residual toner therefrom, blade cleaning is known. In this method, cleaning blades constructed of an elastic member, such as a rubber plate, are used. In blade cleaning, an edge or ridge of the cleaning blade is pressed against the surface of the photoreceptor that rotates, thereby scraping off from the photoreceptor substances, such as toner, adhering thereto. Blade cleaning is widely used for its simple structure and reliable performance.